1. Field of the Invention
The present invention is directed to a device for converting a constant rotational input into a rotational output which is proportional to a separate input signal.
2. Prior Art
A conveyor scale and recorder, which was operated by a belt conveyor and gave a continual record of the weight of material being transported on the conveyor belt, is disclosed in U.S. Pat. No. 3,155,181. The scale had a pair of cones which were mounted with their axes in parallel for rotation, one of the cones was driven by the belt of the conveyor and a transfer means or device was disposed between the cones for transferring the rotation of the one cone to drive the other cone whose output shaft was connected to a counter or recorder. The transfer means utilizes a pair of friction balls which were supported in a race or cage by a plurality of spools and was shifted along the axes of the pair of cones in response to sensed weight conditions on the belt.
The above described scale of the above mentioned patent has met with commercial success but has also encountered several undesirable problems. For example, the friction balls and spools of the cage provide a drag which is undesirable. The friction balls and retaining spools as well as the bearings and journals for the spools in the retainer cage are subjected to wear. Such wear will cause a tendency of the contact points between the cones and their respective friction balls to vary.
In the transfer means of the patent, the action of the surfaces of the cones especially in the areas of high angular contact apply a shifting force to the ball cage which may affect the position of the weight of the weight bar. This force on the weight is undesirable.
In addition, the friction ball and the ball cage require a certain amount of space between the two cones and thus limits a size reduction of the device for small scales. The structure for guiding the cage as it travels in the axial direction along the surfaces of the cones also requires a complicated arrangement of guide bars and supports.